1. Field of the Invention
There have been several major transportation accidents in the United States involving the release of hazardous chemicals, followed by spectacular fires and explosions, dispersion of toxic vapors, extensive property damage and potential ground water pollution. In many of these incidents, there have been injuries to people and/or loss of human life. Property and environmental damage have been estimated in the hundreds of millions of dollars. Many of these catastrophes have involved railroad tank cars and tractor-trailer tank trucks transporting hazardous chemicals. The transportation of hazardous chemicals in the United States on railroads, roads, highways and waterways is regulated by various agencies of the U.S. Department of Transportation, as well as by state and local bodies. These agencies have instituted numerous regulations to reduce accident frequency, severity and public impact of hazardous chemical releases. These regulations stipulate technological modifications as well as operations and management changes in the transportation of hazardous chemicals to provide safety to the public. For example, one regulation requires the carrying of bills of lading or waybills identifying the chemicals being transported. The railroads, for example, have become conscious of potential public hazards and economic costs resulting from accidental chemical releases, and have undertaken changes in operational procedures, development of contingency plans, and have instituted emergency response management procedures to cope with hazardous materials accidents. Truck fleet operators also are considering various operational measures to reduce tractor-trailer accidents involving chemicals.
Unfortunately, major transportation accidents involving hazardous chemicals continue to occur. One of the major problems associated with railroad accidents involving hazardous materials in tank cars (and the consequent release of their contents) is the proper identification of the various chemicals being transported. The National Transportation Safety Board and the National Fire Protection Association have repeatedly pointed out that emergency response personnel need immediate and accurate information concerning the hazardous or other materials involved, and guidance in the handling of transportation emergencies (involving hazardous materials).
The National Transportation Safety Board (NTSB) has pointed out repeatedly in many of its accident investigation reports how the timely determination and initiation of proper response action could have saved lives and property damages. For example, in the report NTSB-RAR-79-1 the Board notes that "Fire fighters experienced a forty-five minute delay in obtaining the waybills and consist information with pertinent hazardous materials emergency information. This delay could have had serious consequences, particularly if they had attempted to fight the fire before the second explosion. Fire fighters should have known immediately where to find the train's hazardous materials information. Also, if the crew members had been injured, a longer delay in obtaining the information would have occurred. If the crew members had been killed or injured, there was no identified location where the consist information could be obtained from."
In 1979, following a train derailment in Mississaga, Canada, the lack of identification of the leaking chemicals for over eight hours led to considerable confusion as to the proper emergency response actions to be taken. Finally, after the chemical was identified as chlorine, over 250,000 people were evacuated--the largest evacuation due to a hazardous materials incident in North America.
The initiation of emergency action in evacuation of inhabitants from potential hazard zones surrounding a train derailment involving several chemical cars in Livingston, La. in 1981 was also delayed by several hours, to almost a day, because of the inability of emergency personnel to identify the chemicals in the derailed cars. Placards attached to the cars identifying their contents were lost, and the car sequences were jumbled as a result of the accident, making identification of contents extremely difficult, even though the way bill for the train was available. There have been several other such incidents involving highway and road trucks in which the single major problem in initiating an emergency response by the first responders on the scene has always been the lack of knowledge of the contents of the damaged vehicles.
2. Description of the Prior Art
Many techniques are available to identify tank cars/tank trucks and their contents. Almost all of these methods are passive in that the information regarding the tank car or its contents is either fixed or cannot be changed easily. Some of these methods include placarding of the tanker contents, bar codes on the tank cars, color coding of tank cars, etc. In the U.S. all bulk containers in transportation containing hazardous materials are required by U.S. Department of Transportation regulations (49 CFR, part 175) to display placards. The placards contain a four digit number (U.S. DOT number or the United Nations number), and have in general symbols in color representing the class of chemicals being transported. Placards and other passive cargo identification techniques have several serious limitations. These include, (i) the information content on the "devices" are either permanent or cannot be changed easily, (ii) the reading of the information can be done only at close range and only when the device is visible, (iii) very limited information can be displayed, (iv) the information on the devices is susceptible to being erased or damaged due to weathering action, chemical spills, and deliberate tampering by third parties,(v) nonuniformity in international conventions on placarding or bar coding, (vi) the "open" nature of the placarding system which allows mischievous elements in society to easily identify highly toxic, dangerous or explosive chemicals being transported through populous areas, which knowledge could be potentially used for criminal acts of violence or to endanger the lives of large numbers of the civilian population. In the case of absence of placards or their loss in accidents the only other method currently available to first responders is to identify the various chemicals in the train or on the tank truck by obtaining the shipping papers (when available) and reading them or to guess the chemical contents from the size and shape of the containers.
Active techniques of chemical identification available at present are useful only if the chemical has been released. These techniques are used for determining the concentration of the chemical in the atmosphere, rather than for strict identification. Most methods used in accident situations rely on remote sensing technologies which utilize electromagnetic radiation in one form or another. Typically, the interaction between the particular chemical in the atmosphere and the radiation emitted by a sensor in the infrared, visible or ultraviolet region of the spectrum is sensed. Identification principles are based on absorption, emission or scattering of spectral characteristics of the radiation. Many systems developed for air pollution studies use laser beams as sources of high intensity coherent radiation.
Other types of identification systems have been described in the literature and in several patent applications for use in commercial and industrial applications for detecting either personnel, objects or transport vehicles. These systems are based on different techniques of data storage (passive cards, magnetic memories, electronic chips), and use different technologies for data communication and detection (light energy, infra red beams, radio frequency signals, etc).
J. H. Auer, Jr., (U.S. Pat. No. 3,377,616), describes a system for communicating information between a moving vehicle and a stationary, way-side receiver. Each vehicle is provided with a transducer device including a suitable transmitting apparatus and a means of extracting energy from the wayside energy source. The transducer is a collection of photoelectric cells each of which is activated according to a pre-determined order by the cutting of a light beam by punched card with holes arranged in particular order to convey one piece of information. As the vehicle passes the wayside energy source, in this case a light beam, the transducer generates a response signal coded in some predetermined manner in accordance with the particular information to be conveyed by each vehicle to a suitable receiving apparatus at the wayside location. This invention is different in principle, range of operation and quantity of information on the transducer. Since the energy source for the operation of the transponder has to come from the light beam, it is essential that for the proper operation of Auer's invention there be (i) relative motion between the vehicle and the wayside device, (ii) the distance between the transponder and the wayside device be very short, of the order of a few feet, and (iii) the transponder "see" the beam. Also, the wayside device has no intelligence and cannot query individual vehicle transponders, nor can it distinguish an individual vehicle transponder and communicate with it on a one-to- one basis in the midst of several other vehicles. The information content on the vehicle units cannot be changed remotely, nor can the change be made easily. The invention of Auer, Jr. is therefore considerably different from the subject invention.
Carroll, et al., (U.S. Pat. No. 4,398,172), describes a vehicle monitor apparatus system for identifying vehicles as they enter a parking lot or a rental car facility. Each vehicle carries an infrared transponder which continuously transmits in the infrared range data on the various parameters related to the vehicle condition. As the vehicle enters a facility, a ground station monitors the transmission from the vehicle transponder and stores the data for print out and other operations. Because of the use of infrared as the transmitting medium, the system is limited to short range, line-of-sight operation only and is susceptible to considerable errors due to humidity and dust, and especially if hot objects are involved. Also, the ground station has no way of manipulating the responses of the transponder on the vehicle because of one way communication. Carrol, et al, refer to the U.S. Pat. No. 4,207,468 of Wilson in which a two way infrared communication between the ground station and the vehicle transponder is disclosed. However, even in Wilson's patent the ground station only turns on and turns off the vehicle transponder, but cannot materially alter the information sent out by the transponder depending on the questions posed by the ground station. In addition, the systems proposed by Carroll, et al., and Wilson do not lend themselves to reprogramming of the "memory" of the vehicle transponder every time the contents of the vehicle changes. These systems cannot be used to identify simultaneously a multitude of cars.
Lennington (U.S. Pat. 4,325,146) and Chiapetti (U.S. Pat. No. 4,338,587) describe other types of vehicle identification systems. Lennington's invention is similar to that of Carroll, et al and is primarily used for allowing a vehicle to pass through a gate depending on the appropriate code stored in the vehicle transponder. Chiapetti's invention is applicable to identifying a vehicle travelling along a lane, such as a highway, for the purposes of collecting tolls, etc. In the Lennington system, a stationary interrogator at the entrance to an area emits optical pulses to activate the transponder on the vehicle approaching the area. Upon such activation, the transponder emits a unique code in the form of optical pulses in accordance with a program stored in its memory. The interrogator then decodes the information and supplies the data to peripheral equipment for checking the authenticity of the vehicle. Chiapetti uses similar principles, except that radio communication is utilized rather than an optical medium as in Carroll, et al, Lennington, and Wilson. None of the above art can deal with identifying vehicles or contents in ensembles of vehicles nor can this art determine the location of a specific vehicle in the ensemble.
Denne and Hook (U.S. Pat. No. 4,691,202) disclose an identification system comprising an interrogator which transmits to a plurality of transponders each of which is arranged automatically to reply by means of a first coded identification signal stored in the transponder memory. The range of operation of the system is limited to about 1 meter. The addressing of each of the transponders is achieved by the unique identification code for each transponder. Very similar techniques of encoding information onto a carrier wave for transmission have been described by Twardowski (U.S. Pat. No. 4,535,333), Walton (U.S. Pat. No. 4,656,472) and Sigrimis, et al., (U.S. Pat. No. 4,510,495). Except for Denne & Hook, the other art is not applicable to communication between and identification of a plurality of transponders. In Denne and Hook, it is essential to know a priori the particular identification signal for each transponder being addressed. Also none of the prior art is suitable for identifying the direction and location of a single unit among an ensemble of units. This need to identify the tank cars and their contents and the pinpointing the direction and location of a specific, user-specified car carrying a dangerous cargo in a jumble of cars occurs when a freight train containing hazardous cargo tank cars derails subsequent to which the cars are lying in all orientations, directions and order.